Non-discoloring flame resistant wool

ABSTRACT

The flame resistance of wool is enhanced by treating it with tetrabromophthalic anhydride, tetrabromophthalic acid, tetrachlorophthalic anhydride, or tetrachlorophthalic acid. The treatment is carried out in an aqueous system in a manner similar to dyeing, or in conjunction with dyeing. In addition to being flame resistant, the treated wool does not become discolored when heated.

United States Patent Friedman et al.

[ Dec. 23, 1975 NON-DISCOLORING FLAME RESISTANT WOOL Inventors: Mendel Friedman, Moraga; John F.

Ash, El Cerrito, both of Calif., Wille Fong, deceased, late of Richmond, Calif., by Yukiye Fong, executrix The United States of America as represented by the Secretary of Agriculture, Washington, DC.

Filed: July 17, 1974 Appl. No.: 489,312

Assignee:

US. Cl. 8/17; 8/128 R Int. Cl. ..D06M 3/02; D06M 13/00;

D06P 5/00; D06P 7/00 Field of Search 8/17, 128 R References Cited UNITED STATES PATENTS 6/1936 l-lochstetter 8/17 7/1967 Koenig 11/1967 Fell et a1 8/17 FOREIGN PATENTS OR APPLICATIONS 744,469 2/1956 United Kingdom 8/128 R OTHER PUBLICATIONS Textile Research Journal, Vol. 43, No. 4, pp. 212-217, April, 1973. Lyons, The Chemistry and Uses of Fire Retardants, Wiley-Interscience, N.Y., N.Y., 1970 pp. 96, 97, 100, 101, 102, 362, 363 and 393.

- Primary ExaminerRonald W. Griffin Attorney, Agent, or Firm-M. Howard Silverstein; Max D. Hensley; William Takacs [57] ABSTRACT 5 Claims, N0 Drawings NON-DISCOLORING FLAME RESISTANT WOOL Description of the Invention This invention relates to and has among its objects the provision of novel modified wool products which are particularly characterized by flame resistance. The objects of the invention also include novel methods for preparing these modified wool products. it is a particular object of the invention to prepare flame resistant wool that does not discolor on heating. Further objects of the invention will be evident from the following description wherein parts and percentages are by weight unless otherwise specified.

Although wool does not ignite readily, flames will propagate in wool once ignition has occurred. A need, therefore, exists to flameproof wool for many uses such as airplane upholstery, carpeting, blankets, sleepwear, and the like. A particular aim of the invention is to fulfill this need.

In the copending application of Mendel Friedman and Willie Fong, U.S. Ser. No. 408,037, filed Oct. 19, 1973, there is disclosed the treatment of wool with chlorendic acid to render it flame resistant. This procedure, however, has been found to have the disadvantage that the treated wool turns brown when heated. We have observed that this is the case whether the wool is dyed or undyed. Thus, when the products produced in accordance with said patent application are heated as in ironing, the fabric rapidly discolors.

We have discovered, however, a means for obviating the above problem. In accordance with the invention, wool is treated with tetrabromophthalic anhydride, tetrabromophthalic acid, tetrachlorophthalic anhydride, or tetrachlorophthalic acid (these compounds being hereinafter collectively referred to as PA) whereby it is not only rendered flame resistant, but also it does not become discolored on heating. This is a surprising aspect of the invention because it would have been expected that PA would cause heat-discoloration of Wool just like chlorendic acid since both PA and chlorendic acid are highly-halogenated cyclic compounds of an acid character.

It is further to be noted that the flame-resistant property of our PA-treated wool is retained despite mild laundering and dry cleaning of this product. The durability of the modification achieved by the invention is believed to be due to the fact that the PA is chemically adsorbed by the wool.

As mentioned above, it is a particular advantage of the invention that wool modified with PA does not discolor on heating. This is the situation whether the wool is dyed or undyed. A particular advantage of the invention is that our flame-resistant products, whether dyed or undyed, can be ironed without discoloration.

Another advantage of the invention is that modification of wool with PA is carried out in an aqueous medium in a manner just like conventional dyeing. In fact, PA may be incorporated in the dyebath either before, during, or after dyeing whereby to achieve both coloration and enhancement of flame resistance.

Another valuable asset of the invention is that the modification does not impair the intrinsic properties of the wool. For example, the treatment does not impair the elasticity, hand, or tensile strength of the textile. The products of the invention are suitable for all the conventional uses of wool, such as fabrication of carpeting, upholstery, and drapery fabrics, garments, etc.

As between the bromine-containing and the chlorinecontaining compounds, we prefer the former (that is, tetrabromophthalic anhydride or acid) as they are the more effective from the standpoint of providing flame resistance. Moreover, we particularly prefer tetrabromophthalic anhydride because it is not only effective but also less expensive than the corresponding acid.

The mechanism of the invention probably involves chemical association between the acid groups of PA and the basic groups of the wool. Where PA is in the anhydride form, it is most likely first converted to the corresponding acid in the hot aqueous treatment liquor before this chemical combination occurs.

In preparing flame-resistant wool in accordance with the invention, the following procedure is used: An aqueous dispersion (i.e., solution or suspension) of PA is prepared. The amount of PA should be at least 2%, based on the weight of the wool to be treated. Usually, about 2-12% of PA, based on the weight of wool, is used. Where the anhydride form of PA is employed, the dispersion is homogenized, i.e., subjected to vigorous and repeated shearing action to reduce the anhydride to a very finely-divided state. Such homogenization facilitates chemical combination between the PA and the wool. We have observed that if homogenization is not applied, the PA deposits on the wool as a loosely adhering powder which is easily lost during subsequent handling with the result that the product has little if any flame resistance. On the other hand, where homogenization is applied to the aqueous dispersion of the anhydride, the resulting product contains PA firmly bonded to the wool so that the product retains its flame resistance during rinsing, winding, handling, and other mechanical manipulations as those involved in fabricating into finished garments or other products, pressing, laundering, dry cleaning, etc.

Having prepared the PA dispersion as outlined above, it is preferably acidified to a pH of about 2 to 4 by the addition of any suitable acid such as sulphuric, phosphoric, acetic, or formic. The dispersion is then heated and the wool entered therein. The dispersion is kept at the boil long enough for the PA to react with the wool. This will generally be about 10-60 minutes, during which time essentially all the PA will exhaust onto the wool and combine therewith. Following this, the treated wool is rinsed with water and dried and is ready for sale or use.

Since the modification of wool with PA is performed under conditions like those used in dyeing, it is preferred to effectuate dyeing either prior to, at the same time as, or immediately following the flame resistance treatment. The addition of PA to a conventional dyebath does not adversely influence the dyeing. In other words, a given dyebath will yield the same level of dyeing if used in conjunction with PA treatment as it will yield in the absence of PA. Thus, in the preferred body of the invention, one proceeds as in conventional dyeing with the added feature that PA is added to the dyebath. This has the advantage that a flame-resistant product is achieved by a minor modification of the usual dyeing operation.

Notwithstanding incorporation of PA in the dyebath, other factors in the dyeing operation are as in conventional dyeing. For example, wetting-out the fibers prior to dyeing, particular dye and adjuvants and the amounts thereof, temperature, and time of dyeing, etc. are selected in accordance with the usual principles of dyeing and thus may be varied over a wide range.

Detailed Description of the Invention In a preferred embodiment of the invention, the following steps are applied.

I. A dyebath is prepared and entered into a suitable vessel which may take the form of a dye beck, package dyeing machine, raw stock dyeing machine, beam dyeing machine, or the like. Typically, the dyebath is formulated by dissolving a dye and dyeing adjuvants in water. The dyeing adjuvants include sodium sulphate,

sodium chloride, sulphuric acid, dispersing agents, and the like. To aid in dissolving the ingredients, the bath is heated, for example, to about 4550 C.

The total volume of dyebath will generally be about to 50 parts thereof per part of wool. The amount of dye will vary depending on such factors as the nature of the dye, the physical state of the wool, and the level of dyeing desired. As the dye, one can use any of the water-soluble dyes useful for dyeing wool such as acid dyes, premetallized acid dyes, etc., all as well-known in the art.

II. The wool to be treated is entered into the dyebath which is then heated to boiling. It may be desired to wet-out the wool prior to entering it into the bath. The wool may be wet-out with water, or more preferably with water containing a small percentage (for example, about 0.01 to 0.05%) of a conventional wetting agent. Following entry of the wool, the dyebath is held at the boil long enough to permit exhaustion and leveling of the dyestuff.

III. PA is then added to the boiling dyebath. The amount of PA used will depend on the nature of the wool textile being treated. Usually, excellent results are attained where one adds PA in the amount of 2 to 12%, based on the weight of fiber (owf).

The preferred procedure for incorporating the anhydride form of PA is as follows: A slurry of the anhydride and a small proportion (e.g., 0.75%) of a dispersing agent is prepared in water at about 60 C. The slurry is homogenized whereby to prepare a very finely dispersed material. The homogenized slurry is then added to the boiling dyebath.

Alternatively, the anhydride may be converted into the acid form of PA before introduction into the dyebath. Thus, the anhydride (and preferably a small proportion of a dispersing agent) are dissolved in water containing l-3% (owf) of alkali, e.g. sodium hydroxide. Acid (for example, sulphuric) is added until a white precipitate is formed. The mixture is heated until the precipitate dissolves. The resulting solution of the acid form of PA is added to the boiling dyebath.

If the PA is already in the acid form it may be incorporated directly into the boiling dyebath as an aqueous solution, preferably one containing a small proportion of a dispersing agent.

After PA is incorporated into the dyebath, heating at 100 C. (or boiling) is continued for a period long enough to attain the desired uptake of PA by the wool. In many cases, this will be about 10-60 minutes.

As in conventional dyeing, it is necessary to maintain intimate contact and relative motion between the fibers and the dyebath and this may be achieved by any suitable means such as stirring, rocking, tumbling, and the like, or by procedures that involve moving the wool about in the bath, or by circulating the bath through the mass of woolen fibers (as in the case with package dyeing machines).

The amount of PA taken up by the wool may be varied by adjustment of such factors as the concentration of PA in the dyebath, and the temperature and time of contact of the dyebath with the wool, and the pH of the bath. In general, the reaction conditions are so selected that the wool adsorbs about 28% (owf) of PA. At such a level of uptake, satisfactory flame resistance is attained.

IV. After completion of Step III, the dyebath is drained out of the dyeing vessel. The wool is then rinsed with warm water to remove excess chemicals used in the treatment. Following the rinse, the treated goods are extracted and dried and are ready for use or sale.

V. The effluent liquors such as the spent dyebath and rinse liquors may be treated to recover the unused PA contained therein. This feature of the invention not only provides economic advantages, but also aids in preventing pollution by recovering what otherwise would be discarded into waterways.

In an alternative modification of the invention, the PA is incorporated into a dyebath as described in Part I, when initially prepared. Then when this bath at the boil is contacted with the wool, the desired dyeing and flame-resistance enhancement are attained concomitantly. In another modification of the invention, the dye is omitted from the bath described in Part I and is replaced by PA. This bath at the boil is contacted with the wool whereby the desired flame-resistance enhancement is achieved. The dye is then added to the bath and contact of the bath at the boil with the wool is maintained until the dye is exhausted onto the fibers.

The invention has wide versatility and can be applied to woolen fibers in any physical condition, e.g. bulk fibers, top, sliver, rovings, yarns, webbing, woven or knitted textiles, felts, garments and garment parts.

EXAMPLES The invention is further demonstrated by the following illustrative examples.

Flame tests were carried out according to the AATCC 34-1969 procedure'published in AATCC Technical Manual, Vol. 48, pages 201-202 (1972).

Ten specimens (3.5 X 10 in.), conditioned at F., I

EXAMPLE 1 A dyebath was prepared by compositing the following ingredients and heating to 49 C.:

Glaubers salt 10% (owf) Sulphuric acid 4% (owf) Conventional dispersing agent 0.25% (owf) Dye mixture 2% (owf) Water to make 1 liter The dye mixture contained 3 parts Calcofast Wool Yellow N (C.I. acid yellow 54), 6 parts Neolan Blue 2R (C.l. acid blue 154), and 1 part Calcofast Wool Pink N (C.I. acid red 186). The pH of the dyebath was about 2-2.2.

A 25-gram wool swatch (plain weave woolen flannel, 6 oz./sq.yd., 10 X 20 in.) was entered into the dyebath which was heated to boiling for about 10 minutes.

Aslurry of 12% (owf) tetrabromophthalic anhydride and 0.75% (owf) of dispersing agent in water was prepared and heated to 60 C. The heated s1urry.was homogenized in a Gaulin Homogenizer and then immediately added to the boiling dyebath. After boiling for 45 additional minutes, the fabric was removed from the solution, washed, and dried.

The so-treated wool swatch was cut into five 3.5 X 10 inch pieces, which were tested for flame resistance, -i the warp direction, as described above.

The procedure as described above was repeated,'and in this case the treated woolswatch was cut and tested, in the till direction, for flame resistance.

In further experiments, the procedures;-- described above were repeated with variation as to the amount of tetrabromophthalic anhydride.

Samples of the untreated wool (control) werete ste'd for flame resistance; Also, the treated products were analyzed for bromine content. l

The results obtainedare tabulated belowf Cone. of tetrabromophthalic anhydride, owf

6 8 10 12 (Control) After flame, sec.

(warp) 31.2 1.4 3.0 1.1 0.4 After flame, sec.

(fill) 31.3 2.8 0.4 0 0.4 Char length, in.

(warp) 10 2.9 3.1 2.3 1.9

(total) Char length. in.

(fill) 10 2.2 1.4 1.6 1.6

(total) Bromine content, 0 3.4 4.3 4.9 5.2

EXAMPLE 2 These experiments were conducted as in Example 1 with the exception that the tetrabromophthalic acid was used instead of the anhydride, and the homogenization step was omitted since the acid is soluble in hot water.

The results are tabulated below.

previously slurried in water with the dispersing agent and homogenized as in Example 1. p I

Swatches of woolfabric were contacted, with agitation, in the bath at the boil for 45 minutes. The fabric was then rinsedin warm water, and dried.

B. Swatches of wool fabric were treated as in Part A, except that the tetrabromophthalic anhydridewas'replaced by chlorendic acid, 12% owf;

The treated samples and a sample of the untreated wool were tested for the effect of heating on'color. In these tests the fabric swatches were heated at C. or C. for 5 or 15 minutes, then testedon a Gardner Mode1 7946' color difference meter. One measurement (R made was the overall reflectance of visible light by the fabric. With this test, a higher value signifies a whiter sample. Another test (parameter a) measures redness (positive values) versus greenness.(negative value). In this test, a higher positive value indicates a redder fabric.

The results obtained are tabulated below:

The results in the above table indicate that untreated (native) wool and wool treated with 12% tetrabromophthalic anhydride exhibit only a very slight color change when heated for 15 minutes at 150 C. On the other hand, wool treated with 12% chlorendic acid rapidly discolors when heated for only 5 minutes at 125 C. and is greatly discolored when heated for 15 minutes at 150 C.

Having thus described our invention, we claim:

1. A process for modifying wool to make it flame resistant, which comprises:

a. contacting the wool with an aqueous dispersion containing about 2 to 12%, owf, of a compound selected from the group consisting of tetrabromophthalic anhydride, tetrabromophthalic acid, tetrachlorophthalic anhydride, and tetrachlorophthalic acid, at about 100 C., and

b. rinsing the wool and drying it.

2. A process for modifying wool to make it flame resistant, which comprises:

a. providing an aqueous acidified dispersion containing about 2 to 12%, owf, of a compound selected from the group consisting of tetrabromophthalic anhydride, tetrabromophthalic acid, tetrachlorophthalic anhydride, and tetrachlorophthalic acid,

b. contacting the wool with the said dispersion at about 100 C. for a period of about -60 minutes, and

c. rinsing the so-treated wool and drying it.

3. A process for concomitantly dyeing wool and for modifying the wool to make it flame resistant, which comprises:-

a. providing an aqueous acidified dyebath containing a wool dye,

b. entering the wool into the dyebath and heating it to the boiling point,

c. adding to the dyebath a compound selected from the group consisting of tetrabromophthalic anhydride, tetrabromophthalic acid, tetrachlorophthalic anhydride, and tetrachlorophthalic acid in the amount of about 2 to 12%, based on the weight of wool, and continuing the boiling until the wool adsorbs about 2 to 8%, based on the weight of the wool, of said compound,

d. removing the treated wool from the dyebath then rinsing and drying it.

4. A process for concomitantly dyeing wool and for modifying the wool to make it flame resistant, which comprises:

a. providing an aqueous acidified dyebath containing a wool dye,

b. entering the wool into the dyebath and heating it'to the boiling point,

c. providing a homogenized, aqueous dispersion of about 2 to 12%, owf, tetrabromophthalic anhydride at about 60 C.,

d. adding the homogenized dispersion to the dyebath, and continuing the boiling until the wool adsorbs about 2-8%, based on the weight of wool, of tetrabromophthalic anhydride, and

e. removing the treated wool from the dyebath, then d. removing the treated wool from the rinsing and drying it.

dyebath, then 

1. A PROCESS FOR MODIFYING WOOL TO MAKE IT FLAME RESISTANT, WHICH COMPRISES: A. CONTACTING THE WOOL WITH AN AQUEOUS DISPERSION CONTAINING ABOUT 2 TO 12%, OWF, OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF TETRABROMOPHTHALIC ANHYDRIDE, TETRABROMOPHTHALIC ACID, AT ABOUT 100*C., AND TETRACHLOROPHTHALIC ACID, AT ABOUT 100*C., AND B. RINSING THE WOOL AND DRYING IT.
 2. A process for modifying wool to make it flame resistant, which comprises: a. providing an aqueous acidified dispersion containing about 2 to 12%, owf, of a compound selected from the group consisting of tetrabromophthalic anhydride, tetrabromophthalic acid, tetrachlorophthalic anhydride, and tetrachlorophthalic acid, b. contacting the wool with the said dispersion at about 100* C. for a period of about 10-60 minutes, and c. rinsing the so-treated wool and drying it.
 3. A process for concomitantly dyeing wool and for modifying the wool to make it flame resistant, which comprises: a. providing an aqueous acidified dyebath containing a wool dye, b. entering the wool into the dyebath and heating it to the boiling point, c. adding to the dyebath a compound selected from the group consisting of tetrabromophthalic anhydride, tetrabromophthalic acid, tetrachlorophthalic anhydride, and tetrachlorophthalic acid in the amount of about 2 to 12%, based on the weight of wool, and continuing the boiling until the wool adsorbs about 2 to 8%, based on the weight of the wool, of said compound, d. removing the treated wool from the dyebath then rinsing and drying it.
 4. A process for concomitantly dyeing wool and for modifying the wool to make it flame resistant, which comprises: a. providing an aqueous acidified dyebath containing a wool dye, b. entering the wool into the dyebath and heating it to the boiling point, c. providing a homogenized, aqueous dispersion of about 2 to 12%, owf, tetrabromophthalic anhydride at about 60* C., d. adding the homogenized dispersion to the dyebath, and continuing the boiling until the wool adsorbs about 2-8%, based on the weight of wool, of tetrabromophthalic anhydride, and e. removing the treated wool from the dyebath, then rinsing and drying it.
 5. A PROCESS FOR CONCOMITANTLY DYEING WOOL AND FOR MODIFYING WOOL TO MAKE IT FLAME RESISTANT, WHICH COMPRISES: A. PROVIDING AN AQUEOUS ACIDIFIED DYEBATH CONTAINING A WOOL DYE, B. ENTERING THE WOOL INTO THE DYEBATH AND HEATING IT TO THE BOILING POINT, C. ADDING TETRABROMOPHTHALIC ACID IN THE AMOUNT OF ABOUT 2 TO 12%, BASED ON THE WEIGHT OF WOOL, TO THE DYEBATH, AND CONTINUING BOILING UNTIL THE WOOL ADSORBS ABOUT 2 TO 8%, BASED ON THE WEIGHT OF WOOL, OF TETRABROMOPHTHALIC ACID, AND D. REMOVING THE TREATED WOOL FROM THE DYEBATH, THEN RINSING AND DRYING IT. 